Bill O'Reilly vs. George Will feud keeps simmering

Last week's on-air tussle between Bill O'Reilly and George Will has apparently been brewing for some time -- and the feud is showing no signs of letting up.

On his show Monday night, O'Reilly essentially confirmed the longstanding bad blood between the two.

"Based upon [Will's] remarks over the years, he sees me as a vulgarian...So there is little common ground between us," O'Reilly said.

Will, a Fox News contributor, wrote a withering review last week of O'Reilly's latest best selling book, "Killing Reagan," accusing the author of slandering the 40th president.

Will followed that up Tuesday with another column that took aim at O'Reilly and the book.

"Were the lungs the seat of wisdom, Fox News host Bill O'Reilly would be wise, but they are not and he is not," Will begins his latest column. "So it is not astonishing that he is doubling down on his wager that the truth cannot catch up with him. It has, however, already done so."

Will called out what he suggests was shoddy research that went into the book and other histories O'Reilly has written, saying, "O'Reilly's vast carelessness pollutes history and debases the historian's craft."

His latest column reiterates points that Will made last week, objecting to the centerpiece of the book, a memo questioning Reagan's mental capacity to continue carrying out the duties of the presidency, as well as O'Reilly's decision to not interview members of Reagan's cabinet.

According to Will, neither O'Reilly nor his co-author Martin Dugard ever saw the memo, nor did they use any resources available at the Reagan Library. O'Reilly said last week that he didn't interview those members of the Reagan White House because they have "skin in the game."

"His is an interesting approach to writing history: Never talk to anyone with firsthand knowledge of your subject," Will wrote of O'Reilly on Tuesday.

Will's column last week earned him an invitation on the "O'Reilly Factor," and the result was a cable news interview crackling with fireworks.

But it was a rare appearance for Will on the "Factor," the top-rated show on Fox News, something that O'Reilly addressed on the show on Monday.

"You may have noticed Mr. Will does not appear on the 'Factor,'" O'Reilly explained as he fielded questions from viewers. "That's because his elitist presentation doesn't fit our format. Nothing personal."

O'Reilly's interview with Will on Friday night certainly got personal. The two debated the factual accuracy of "Killing Reagan" while taking shots at each other's credibility.

Will said O'Reilly was "something of an expert in misleading people," while O'Reilly derisively called Will a "hack." O'Reilly also said that Will had broken a promise to Fox News executive producer Michael Clemente.

According to O'Reilly, WIll had told Clemente that O'Reilly would get a call before the column was published. Will said O'Reilly had his facts wrong.

"It would not be the first time you got something wrong," he told O'Reilly.

A Fox News spokesperson did not respond to a request for comment.

In a separate appearance on Fox News last week, Will said that O'Reilly was "unhinged" during the interview.